United States Patent Classification system

The United States Patent Classification (USPC) system defines hundreds of codes to identify technology categories fitting a patent application. From (year) to 2013, U.S. patent examiners applied these codes to patent applications partly to direct the examination work within their agency, and to assist people searching for patents later. They've partly switched away from this system to the CPC system to achieve international comparability.

The overall layout of the code numbers and their meanings can be found from here: https://www.uspto.gov/web/patents/classification/selectnumwithtitle.htm

US patent classes are associated with an officially defined difficulty, and patent examiners are allocated more time to evaluate patent applications in difficult/slow categories. (more to come; see Frakes paper.)

Classification Standards and Development

A division of the USPO/USPTO works on classification standards. It's called the Classification Standards and Development, or CSD, division. It is part of the OIPC (Office of International Patent Cooperation).

• Contact numbers
• Handbook of Classification (undated)

Updates to fold in

Since June 2015, U.S. utility patents are published with CPC codes but no longer with USPC codes. Design patents and plant patents still have USPC codes. "US patent documents first published with CPC codes in November of 2011." "CPC has about 250K subdivisions, and the USPC has only about 150K." "there is a provision in the CPC rules to list CPC classes in a descending order of relevance" In a USPC list, a most-relevant category may be listed in bold.

From Examiner Handbook, Appendix A: USPTO's "philosophy on the organization of patent data was formulated in early 1964 and was set forth in the publication Development and Use of the Patent Classification Systems (DUPACS) which was issued in January 1966 and is now out of print. The publication United States Patent Classification Standards and Practices (USPCLASP) has replaced DUPACS."

• Examiner Handbook (for USPC), online, undated, perhaps 2013-2014: [1]
• Appendix A quoted just above: [2]
• Overview of the USPC, Dec 2012, 6pp: [3]

Letter suffixes

A letter may appear at the end of a classification, e.g. USPC 244/45A and USPC 244/45R. These mark a temporary division of these patents, which we are not carefully tracking here, based on advice from a specialist at the US PTO (per the discussion at Talk:USPC 244/35). It is possible that the 45As were for patents with "compressed airflows and the 45Rs for all residual others.

Mappings and concordances to and from IPC and CPC systems

• note of UPSC-CPC concordance
• Search to get to USPC-IPC concordances

DIG categories

• Classifications like USPC 52/DIG.10 are called digests. "Digests are similar to cross-reference art collections, but they do not have definitions. The identifiers for digest subclasses all begin with 'Dig', and are followed by a one- to three-digit number. Digests appear at the very end of the schedule after a header identifying them and are only superior to other digest subclasses indented under them.

These may be like "tags" or "keyword" categories, that is, substantive labels with non-exclusive categories.

History

Source: Goodbody's Patent classification through the ages

• An early U.S. classification "was used to place the models and applications in groups based on general topics, [enabling] examiners and staff to efficiently search."
• "By 1830, the US [patent system had] 16 broad classification categories." They were used to organize materials and to determine which examiner would look at an application.
• "In 1836, the New Patent Act included the first statutory mention of a patent classification system [for] models and applications."
• 1867: the number of classes rises from 22 to 36.
• 1872-3: 145 classes, citing Commissioner Leggett
• As of Jan 1, 1878, the number of U.S. classes grew to 158.
• "The German Patent Office put a class on their patents as early as 1877."
• In 1880 the U.K. patent office created their classification system.
• 1899: a Patent Classification Division (at USPO probably), added a level by creating subcategories of class 20, Wooden Buildings
• In 1900, U.S. Frank C. Skinner, head of the new Classification Division, published the Plan of Classification of Patented Inventions. "This became the basis for the United States Patent Classification (USPC) system from that point forward."
  

  Until 1909 aerial navigation was a category with Class 98, pneumatics. (Division 2, examiner Rafter.) In 1909–1910 it was granted a new category, USPC 244.
  • "The plan specified that “articles of manufacture will be grouped according to their function or use… not to select a specific or limited function as the basis of classification where the articles are capable of a broader use.”
  • "The US thus moved to grouping according to function or use. Before that, the groupings were based on broad categories such as agriculture, boating, and other categories."
  • Note: This publication seems hard to find today. It's available on microfilm from some university libraries. 16 pages.
• The Office of International Patent Cooperation (OIPC or perhaps DCIPC) started in 2014. This is probably part of USPTO. OIPC is right on this poster. Possibly it was published by OIPC although her affiliation is listed as CSD which might be classification division.

See also

• CPC tutorial by Matt Troyer
• USPC definition on Wikidata
• Revised Classes and Subclasses of Subjects of Invention in the United States Patent Office, arranged in numerical order: a supplement to the Manual of Classification Revised to January 1, 1912. (Scan at Internet Archive.) This would be a good source for counting the number of subclasses as this point in time; and it gives short descriptions of each, as well as cross-references.

Enclosing categories	US patent classification systems
Subcategories	USPC 70, USPC 104, USPC 244, USPC 446
Keywords	CPC, IPC, French patent classifications, German patent classifications, NBER patent classification, Simple tech terms
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